There are many names commonly used interchangeably for the monofilament line used for cutting vegetation, not limited to the following: trimmer line, weed trimmer line, grass trimmer line, monofilament line, string trimmer line, strimmer line, cutting line, line, line strips, strips, flails, and weed whacker line. Monofilament line is sold in many different cross-sectional shapes and is made from many different types of nylon plastic.
The prior art, including U.S. Pat. Nos. 7,603,782 and 7,743,511 (hereby included by reference for their teachings), discloses trimmer heads with line holding mechanisms (line holders) capable of pivoting on a vertical axis. There are many names commonly used for these line holders including, but not limited to posts, pivoting line holders, pivoting posts, pivot posts, line holding mechanisms and pivoting line holding mechanisms. All of these terms may be used interchangeably. These terms are used with line holders that are all designed to pivot about a vertical axis. However, some of these terms are also used with line holders that are not designed to pivot.
The prior art discloses a pivot post having a flange at the bottom of the post. This post is operatively connected to the trimmer head housing by loosely sandwiching the post's flange between a lower head portion (cover) and an upper housing portion of the trimmer head. The post is held such that its relative position on the head is fixed, the pivot post can rotate 360 degrees about a central vertical axis, but it cannot move vertically.
Certain commercialized products incorporating pivoting posts include line-holding mechanisms having the basic shape of a round post with a circular flange at the lower end. The top end of the post is beveled (slanted) on two opposite sides with two straight-through passageways for insertion of the trimmer line, where the passageways connect the two beveled portions. A representation of these prior art commercially available posts can be found as reference numeral 50 of the '511 patent.
Some of the commercially available trimmer heads utilizing the construction method of sandwiching the pivot post flange between lower and upper head portions include the PivoTrim™ X2, PivoTrim™ Ugly™ Head, and the PivoTrim™ Classic, PivoTrim™ Pro, and the PivoTrim™ Hybrid. These products are sold by Shakespeare Company, LLC.
The prior art also discloses pivoting line holders which mount to the top surface of the trimmer head and are assembled to the trimmer head housing using threaded fasteners such as bolts. These line holders pivot about the axis of the fastener. The trimmer line is completely held at the periphery of the holder and the center of gravity of the holder is not aligned with the axis of rotation.
The prior art further discloses a trimmer head which builds upon this latter type of pivot post design and is disclosed in U.S. Publication 2014/0202009, hereby disclosed by reference. This trimmer head requires custom manufactured fasteners which are intended to be periodically removed and reinstalled by the consumer to allow the use of blades instead of line holders.